1. Field of the Invention
The present invention relates to an improved filter, and more particularly to a gross filter for use in a drainage device. Specifically, the present invention relates to a gross filter with an open face that is configured to lessen filter blockage by gross particulate matter, for example blood clots, entrained in incoming fluid while also permitting a clear view of blood clot volume retained inside the filter.
2. Prior Art
Gross filters for use in filtering out large particulate matter entrained in body fluids drained from a patient during convalescence or post-operative recovery are well known in the art. Typically, gross filters of this kind are incorporated in a drainage device, for example a Chest Drainage Unit (CDU), for filtering blood clots and other gross contaminates from body fluids before reinfusing such fluids back to the patient.
A CDU is an apparatus for suctioning gases and liquids from the pleural cavity of a patient in order to re-expand the patient's lungs. The pleural cavity lies within the rib cage above the diaphragm and is surrounded by the pleural membrane. The pleural cavity contains both lungs, which in their normal expanded state fill the pleural cavity. Several conditions and diseases such as interventional surgery, trauma, emphysema and various infections can cause a build up of liquid and gases around the lungs in the intrapleural space. When this happens, it causes the lungs to collapse to a volume much less than that of the pleural cavity, thereby severely impairing breathing functions of the patient. The lungs can be re-expanded to their normal state to fill the pleural cavity by draining the liquid and gases from the intrapleural space using the CDU. A typical CDU and its operation is disclosed in U.S. patent application Ser. No. 08/810,056 to Swisher et al. entitled "Chest Drainage Unit with Controlled Automatic Excess Negativity Relief Feature", assigned to the assignee, and is herein incorporated by reference in its entirety.
During the draining of fluid from a patient's pleural cavity blood clots may develop and become entrained in the fluid as it enters the collection chamber of the CDU for eventual reinfusion to the patient. During reinfusion of blood, it is desirable that the collected blood be free of any large particulate matter or other kinds of gross contaminants before entering and collecting at the bottom portion of the collection chamber. In order to screen out these undesirable contaminants a gross filter is provided near the inlet to the collection chamber for filtering out large particulate matter as fluid enters the CDU. The Swisher et al. device referenced above is generally exemplary of medical drainage devices that incorporate a gross filter for filtering out blood clots and other large particulate matter from fluid drained from a patient's pleural cavity. The gross filter used in the Swisher et al. device comprises a porous filtering material placed near the inlet of the collection chamber in a horizontal orientation so that all incoming fluid must pass through the gross filter before collecting in a pooling area located at the bottom portion of the collection chamber. In this manner, incoming fluid is filtered prior to entering the pooling area so that blood clots and other large particulate matter are retained on top of the filter.
Unfortunately, the gross filter of the Swisher et al. device suffers from several drawbacks. First, blood clots that are filtered out and retained inside the gross filter will begin to block and impede the flow of fluid being filtered as blood clots begin to accumulate and spread over the surface area of the filter, thereby wasting blood that could be reinfused back to the patient. Second, the gross filter of the Swisher et al. device is made from a reticulated foam material which has a tendency to separate into smaller fragments when trimmed for the size required to properly fit into the collection chamber, thus causing possible contamination of already filtered fluid by these separated fragments.
As of yet, nothing in the prior art has addressed the problem of developing an improved gross filter made of a solid unitary construction that advantageously prevents total blockage of the filter by gross contaminants while also addressing the need for a gross filter that permits clear viewing and accurate visual measurement by medical personnel of the volume level of gross contaminants retained in the filter.